Mounjaro and pregnancy

Mounjaro is a weight loss injection that belongs to the glucagon-like peptide 1 (GLP-1) agonist family of medications. This means it works similarly to the natural hormone GLP-1.

The active ingredient in Mounjaro, tirzepatide, makes the body think there are high levels of GLP-1 and another hormone called glucose-dependent insulinotropic polypeptide (GIP).

The body responds by slowing down stomach emptying, telling the brain it’s full, and regulating glucose (sugar) levels in the blood. This causes people to feel fuller for longer and eat less, helping them to lose weight.

Mounjaro is unique as it targets 2 hormone pathways rather than 1, which can lead to impressive weight loss results. However, the medication is not suitable for everyone. A doctor should always review your medical history and any medications you take before prescribing Mounjaro.

There is very limited evidence on whether Mounjaro affects pregnancy. Because of this, Mounjaro is not recommended if you are:

• pregnant
• trying to get pregnant – if you decide this while on Mounjaro, it must be stopped at least 1 month before trying
• able to get pregnant and are not using contraception

Why can Mounjaro not be taken during pregnancy?

Without enough evidence to say whether they’re safe or not, many drugs are avoided during pregnancy. This is because drugs can cross the placenta and reach the baby. Often, the medication does not harm the baby, but sometimes it can.

Drugs are sometimes not recommended during pregnancy because studies have found there’s a risk to the baby, but often it’s because we do not have any evidence about whether it’s safe or not.

Taking some medications during pregnancy can harm the developing foetus and affect its development, or impact the mother’s health. This means it’s not ethical for us to test medications on pregnant women in case something happens to harm either of them.

Is there any research on Mounjaro and pregnancy?

There is a very limited amount of research on Mounjaro and pregnancy.

Studies in animals found that Mounjaro caused birth defects and reduced growth in foetuses. We do not have similar studies in humans to say whether the same thing might happen, but due to these animal study findings, Mounjaro should not be taken during pregnancy.

The only data we have about pregnant women taking Mounjaro is from clinical trials where women became accidentally pregnant. Of 4,701 women involved in clinical trials, 6 women taking Mounjaro became pregnant.

Of the 6 pregnant women who were taking Mounjaro, there was:

• 1 healthy child
• 1 spontaneous abortion (miscarriage)
• 1 ectopic pregnancy
• 1 elective termination (voluntary abortion)
• 2 pregnancies with no outcomes reported

As this is such a small group of women, it’s not possible to draw any conclusions about the impact Mounjaro has on pregnancy at the moment. More data may be available in the future, but for now, Mounjaro should not be taken during pregnancy.

Yes, if you plan to start trying to get pregnant, you should stop taking Mounjaro at least 1 month before you plan to get pregnant. This should give you long enough to break down and remove the drug from your body.

You may choose to stop taking Mounjaro even longer in advance if you feel more comfortable doing this.

If you get pregnant while taking Mounjaro, do not take any more of the medication and contact your doctor straight away. They will need to report the situation to an organisation that monitors drug toxicity during pregnancy.

You will be offered a standard, detailed scan at 20 weeks to check that your baby is developing properly, but usually no extra monitoring is needed.

There are some reports of women who were taking GLP-1 medications like Mounjaro who accidentally got pregnant and then stopped taking the medication immediately. These reports have not raised concerns about the baby being harmed by Mounjaro, but more research is needed to say for sure.

Whether you can start taking or restart Mounjaro after giving birth depends on your general health and whether you’re breastfeeding.

If you’re breastfeeding

Tirzepatide (Mounjaro’s active ingredient) is a large molecule, so it’s unlikely to pass into breastmilk in large amounts, but ultimately, we do not know this for sure. It may be able to enter breastmilk and be absorbed by a breastfeeding child, which could be harmful for them.

If you’re breastfeeding and would like to start Mounjaro, it’s important to discuss this with a healthcare professional. You may be advised to stop breastfeeding if you’re sure you want to take Mounjaro, but it’s important to be aware of the benefits of breastfeeding as well as the risks and benefits of Mounjaro before making a decision.

For example, Mounjaro can cause side effects like feeling or being sick, so if you’re still recovering from giving birth and looking after your baby, it may be difficult to manage if you do get side effects.

If you’re bottle feeding

For women who are exclusively bottle feeding their child, you may be able to start taking Mounjaro if you’re otherwise healthy. However, this should always be discussed with a doctor.

If you or your partner are trying to get pregnant, it’s worth considering that Mounjaro’s impact on fertility is still unclear. Talking things through with a doctor may help you decide whether you want to take Mounjaro if you’re trying to conceive.

Male fertility

When it comes to male fertility, Mounjaro may not always have a positive impact. There is still very little research into how GLP-1 medications affect sperm quality, male hormone levels, and general fertility. One study found that liraglutide, another GLP-1 medication, can negatively affect sperm count, while other studies have found no changes in sperm measurements or hormone levels.

Female fertility

Studies have not been conducted to see whether Mounjaro impacts fertility directly, in men or women. But there is some evidence that losing weight can help women struggling with infertility.

By helping with weight loss, Mounjaro may make it easier for women to get pregnant. A recent report by the Guardian found that 40 unexpected pregnancies have been reported to the UK watchdog in women taking GLP-1 medications.

As this has happened recently, there are no published studies to confirm the effects these drugs are having on fertility. But experts believe the cases of previously infertile women becoming pregnant could be due to the weight loss effects of the medication. It may also be down to GLP-1 medications making the contraceptive pill less effective.

Yes, Mounjaro slows down how quickly the stomach empties, which can affect how your body absorbs the contraceptive pill even if you take it perfectly.

This can make the pill less effective and increase your chances of getting pregnant. As Mounjaro should not be taken during pregnancy, it’s important to do everything you can to avoid pregnancy while taking this medication.

For the best protection, it’s best to switch to a method of contraception that’s not a tablet, like the implant, vaginal ring, or the hormonal or copper coil.

Alternatively, you could use a barrier method of contraception alongside the pill. You should use a barrier method for the first 4 weeks after starting Mounjaro, and then for 4 weeks after each dose increase.

Mounjaro can be an effective weight loss medication, but it should not be taken during pregnancy. It’s always best to speak to a doctor if you’re taking Mounjaro and want more information on how it affects pregnancy.